[BUG] Session broken -> API Error: 400 {"type":"error","error":{"type":"invalid_request_error","message":"The request body is not valid JSON: no low surrogate in string: line 1 column 410559 (char 410558)"}}

Also experiencing this

Possibly related https://github.com/anthropics/claude-code/issues/1701

it happened again in the next session. Seems to happen when editing large files. At least it happened just now in the new session when editing the same large file (a markdown file with ~1700 lines).

edit:

i downgraded to 1.0.9 and claude was able to do multiple edits to the same file with auto-accept edits on

same problem

Just experienced it when editing a file

Happens to me as well. Latest version - 1.0.55. In my case it wan't a large file.

It helped me to press Esc twice and select one of the previous queries.

Hitting this issue about once every 24 hours on my Macbook.

Have you tried running "/clear" or opening a new terminal (killing the old claude session)? I think it's an internal error where it doesn't manage some part of the memory well. It doesn't compact, it just dies with the MCP plugin. I was using playwright and it started happening.

Same here issue here.

Same issue facing here as well

Just hit this as well. Tried restarting my terminal session, and logging out and back in.

Clearing the session is not really an acceptable fix if you're in the middle of something, all of the previous context dissappears which is very problematic in the middle of claude applying iterative fixes

Still occuring. WSL 2, debian, CC v2.0.1
Seems to happen after calling playwright or serena mcp for me. After which my session is hosed and I can't send any more messages.

<img width="1461" height="287" alt="Image" src="https://github.com/user-attachments/assets/4889cfd7-0ebe-4eda-b5eb-1c4de5741c3a" />

It happens again in Claude Code v2.0.10. I'm using the latest version of Claude Code extension in VSCode.

Still happening (MacOS 15.6.1, Claude Code 2.0.14) :-(

Context: developing a tool (Typescript) to sanitise text containing unicode-based pseudo-formatting
=> when the context contains certain unicode characters it obviously breaks the API.

Desired behaviour: Claude's API is able to process the full Unicode character range

This issue has been inactive for 30 days. If the issue is still occurring, please comment to let us know. Otherwise, this issue will be automatically closed in 30 days for housekeeping purposes.

I encountered this while using Claude Code with a custom MCP server. The failing request was a task.update call where the description contained Unicode characters (✅, ⚠, →) and markdown formatting. The error occurred mid-session; starting a new session and re-running the identical command worked fine.
This suggests the corruption accumulates in the session state rather than being caused by specific input content — the same Unicode-heavy payload succeeds in a fresh session but fails in a longer-running one.

This issue has been automatically closed due to 60 days of inactivity. If you're still experiencing this issue, please open a new issue with updated information.

This issue was closed incorrectly despite recent human comments. This behavior of the bot is reported at https://github.com/anthropics/claude-code/issues/16497. Please upvote that issue, so maybe it gets noticed.

This issue has been automatically locked since it was closed and has not had any activity for 7 days. If you're experiencing a similar issue, please file a new issue and reference this one if it's relevant.